Sleep Disturbances Heighten Pain

April 2, 2007 -- It may come as no surprise to new parents, but getting up
throughout the night may actually be painful.

A new study shows that frequent sleep disturbances, like getting up to care
for a crying baby, may affect the body’s natural pain inhibitors and increase
spontaneous pain among women.

“This study finds that fragmented sleep profiles, akin to individuals
suffering from middle of the night insomnia, health care workers on call, and
parents caring for infants, alter natural systems that regulate and control
pain, and can lead to spontaneous painful symptoms," says researcher
Michael T. Smith, PhD, of Johns Hopkins University, in a news release.

Researchers say the results suggest that frequent sleep disturbances, not
just sleep deprivation, may affect how women perceive pain and play a role in
chronic pain conditions.

Sleep Disturbances May Be Painful

In the study, published in Sleep, researchers controlled the sleeping
patterns of 32 healthy women for seven nights and compared their pain
symptoms.

All the women slept undisturbed in a sleep lab for the first two nights.
Then the women were divided into three groups for the nights three through
five. The first group slept undisturbed for eight hours, the second group was
awakened once an hour for eight hours, and the third group was sleep deprived
with a delayed bedtime.

On the last two nights, both the disturbed sleep group and the
sleep-deprived group were deprived of sleep for 36 hours followed by an 11-hour
recovery sleep.

Throughout the study, researchers assessed the women’s pain thresholds and
pain inhibition.

The results showed that only the women in the disturbed sleep group
experienced an increase in spontaneous pain and decrease in pain
inhibition.

"Our research shows that disrupted sleep, marked by multiple prolonged
awakenings, impairs natural pain control mechanisms that are thought to play a
key role in the development, maintenance, and exacerbation of chronic
pain," says Smith.